Electrophoresis generally involves the placing of a sample substance, such as blood serum or urine, in a support medium. An electric potential is applied across the medium via electrodes, causing colloidal particles in the sample substance to migrate toward one or the other of the electrodes. The rate of migration is determined in part by the electrical charges on the particles in the sample substance, the composition of the support medium, and the magnitude of the imposed electrical potential. Particles with similar properties tend to separate into defined areas or bands on the support medium and thus a determination can be made as to the amount of each class of particles present in the sample. A graph or analog curve of the relative densities of these areas or bands can provide information as to the relative proportions of each which are contained in the sample substance. Such electrophoretograms provide important information as to blood serum, urine, cerebrospinal fluid, or other biological fluid composition which may be used by clinical pathologists or the like to assess a patient's condition.
A technique has been recently developed that provides improved separation of the sample substance on the medium. This technique, often known as high resolution electrophoresis (HRE), uses an agarose medium or gel and a modified buffer containing calcium ions. The HRE technique also employs relatively higher electric potentials across the gel than conventional electrophoretic techniques.
A difficulty with HRE, however, is that the higher voltage causes heating in the gel. If sufficient heat is generated, the gel and the resulting electrophoretogram may be damaged or destroyed. To overcome medium heating, it is known to cool the gel while the higher voltage is applied. For example, a cooled electrophoresis cell is available from Corning Medical, Corning Glass Works, Palo Alto, Calif. The Corning cell includes a gel holder which shares a common wall with a tank into which ice, a cooling liquid or a liquid/ice slurry may be placed. The holder retains the gel such that a portion of the gel is pressed against the common wall.
The Corning cell, however, has several drawbacks. For example, the common wall is significantly shorter than the gel along the direction that the electric currrent is applied. Thus a relatively limited portion of the gel is actually held against the common wall where maximum cooling can take place. Furthermore, the gel holder can accept only a single sized gel in the direction that electric current is applied. Lastly, the tank includes a small access hole that makes it difficult to fill or empty the tank.
Thus there is a need for a cooled cell that overcomes the limitations of the Corning cell, providing a conveniently used, efficient cooled cell for use in electrophoresis.